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Remove Anything from Metal 



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Remove Anything from Metal 



Written By: John Todd 



TOOLS: 



Drill (1) 
Tinsnips (1) 
Wire brush (1) 
Wire cutters (1) 



PARTS: 



Bucket (1) 

Sodium carbonate (1) 
Used for fabric dyeing and adjusting pH. 
it's available from craft, aquarium, and 
home improvement stores. I paid $6 for 
a 21b jar of Balance Pak 200 at a pool 
supply shop. 

Rods (4) 

for the anodes. Carbon rods last much 
longer. Do not use stainless, chrome, or 
galvanized steel, which will leach out 
toxic chromate. 

Gutter leaf guards (3) 

RodCl) 

Washer (1) 

Rod butt joint (1) 

Ceiling hook (1) 

Nut(1) 

Battery charger (1) 

If your charger's ammeter doesn't go up 



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Remove Anything from Metal 



or its hum doesn't increase when you dip 
your part into the bath, you may need an 
older, "dumber" charger without a safety 
interlock, that won't test whether it's 
connected to a battery. 

Wired) 

Zip ties (30-50) 

Water (1) 

Solder (1) 

for soft-clamp anode connection 



SUMMARY 

I love using old machine parts for my projects; often their workmanship surpasses that of 
anything new, and you can get them cheap or even free. Find a junkyard full of ancient, rusty 
industrial equipment, and you can build almost anything — or at least be inspired to, which is 
half the battle! 

But many older machine parts, especially cheap ones, have rust, paint, or other coverings 
that make them ugly and difficult to work with. Over the years, my salvage habit has turned 
me into something of an expert in amateur metal restoration. I am by no means a 
metalsmith, but I have collected a library of easy techniques that can enable any moderately 
equipped hobbyist to turn neglected lumps of metal into shiny, working components. 

Rust, the oxidation of iron, takes up far more volume than the metal it grows from, so the 
parts underneath look surprisingly undamaged after treatment. The same goes for old paint, 
which protects the surfaces underneath it. 

There are 3 basic ways to remove oxidation or paint from metal in a home shop: mechanical, 
chemical, and electrochemical. (Thermal methods, and exotic techniques like dry ice 
blasting, molten salt dips, and bacterial siderophores, require specialized equipment.) Here I 
describe some home methods, and how to construct one of the most effective rust-removal 
tools of all: an electrolytic conversion tank. 



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Remove Anything from Metal 



Step 1 — Use mechanical methods. 

• These work well for smooth surfaces with paint or other coatings, and some light rust. For 
surfaces with cracks, pits, or fine texture, the only effective mechanical method is 
abrasive blasting (aka sandblasting). But to get into the cracks, you can also follow other 
mechanical methods with chemical methods. 



A 



• Safety first: In the shop, I almost always wear leather gloves. A minor slip with a 
12,000rpm wire brush will lead to a discouragingly wasted day at the emergency 
room. 

• I wear goggles 100% of the time that I'm working with any type of tool or liquid. It's 
easier to just leave them on rather than trying to remember, do I have them/where are 
they/do I need them for this task? 

• Some of the chemicals used here have nasty fumes, so don't use more than you need, 
and use chemicals outdoors, where there is less risk of fume buildup. 

• Keep a fire extinguisher handy, in case sparks or other heat sources cause flames. A 
related hint: Do not grind surfaces that are still wet with flammable cleaning liquid. Learn 
from my mistakes! 

• Wear respiratory protection when using mechanical methods. 



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Remove Anything from Metal 

Step 2 

• Sandpaper Use on smooth, painted surfaces in good condition with no corrosion. Good for 
preserving delicate metal. 

• Start with heavy grits (80) and work down to a finer grit (200). Always sand wet — 
submerged or under a constant stream of water — to prevent the paper from clogging. 

• Steel wool Removes superficial "flash" rust, surface imperfections, powder coats, and 
some thinner paint layers. Very fine wool (#000) will also remove stains from chrome and 
even windshield glass without noticeable scratching (but experiment first). 

• Scouring or sanding pads (manual) Remove organic residues such as grease or oil 
buildup on engines, or sticker or tape gunk (use with solvent). Good for mild to medium 
surface rust in some cases. 

• 3M scouring pads are the only good ones I've found. 

• Scouring pad discs (powered) At 13,000rpm, these discs are darn near miraculous 
against paint and light rust on any large, smooth surface. 

• Use scouring pads rather than sanding pads, which will sand away the metal itself. A 
die grinder will spin them faster and work better than a drill. 3M makes effective Roloc 
brand pads for die grinders. You can also try my hack of attaching a cutout rectangle of 
manual scouring pad to the bottom of an orbital sander in place of paper, which works 
wet or dry for cleaning boats, awnings, outdoor furniture, etc. 



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Step 3 




• Angle grinder with wire cup brush A low-cost, fast way to clean rust, paint, or other 
coatings from reasonably wide-open surfaces on large parts (see photo). 

• Will gouge aluminum and other soft metals and leave swirl marks on most steel. Very 
noisy and dusty, and wires can fly off and embed into arms, legs, etc. Less effective 
alternatives: drill with a wire brush bit, bench-mount wire brush grinder. 

• Angle grinder with flap wheel Reduces thick paint buildup or heavy rust over large, flat 
areas. Best as an initial prep step. Removes everything rapidly, including the metal itself, 
so be careful! 

• Wire brush (manual) Removes petrified grease from vehicle parts. Helps remove loose or 
powdered oxidation alongside other, more effective methods (second photo). 

• Needle scalers These earsplitting devices have an array of thin, hard rods that 
successively slam forward a few millimeters with each stroke. They are effective at 
removing rust and paint, but care must be taken when used on thin or soft metal. The 
metal can be dented or pitted by the needles. They are usually air powered. 



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Remove Anything from Metal 



Step 4 



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• Abrasive blasting Excellent for 
removing paint, rust, or other hard 
imperfections from any surface, 
though less effective against softer 
coatings like rubberized paints or 
heavy grease (see photo). 

• The downsides are that this 
method is messy and the 
equipment is expensive. You 
can use a 5hp/50gal air 
compressor ($200 on eBay or 
Craigslist) with a small blasting 
gun, but more power and volume 
are better. A $100 benchtop 
blasting cabinet will speed the 
process, keep you clean, and 
save you from having to sweep 
up abrasives from your 
driveway. 

• Do not use actual sand, ever, for 
"sandblasting," due to the risk of 
silicosis. Safe abrasives include 
glass beads ($20 for 25lbs), 
aluminum oxide (more 
aggressive; $50 for 25lbs), and 
ground walnut shells (gentler but 
slow; $25 for 25lbs). While 
blasting, keep dust out of your 
lungs by wearing a real 
respirator with replaceable 
filters, not a disposable mask. 

• Moisture in your compressed air 
will cause more rust later. A 
good cheap hack is to coil a long 
length of the hose through a 



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Remove Anything from Metal 



trash can full of cold water and 
install a water trap at the 
downstream end. 

• Filter your abrasive medium 
thoroughly for reuse with a good 
sieve, or a series of 2 with 
decreasing mesh size. Paint, 
grease balls, or other impurities 
recycling through your gun will 
quickly lead to poor performance 
and require gun disassembly. 

• Soda blasting This newer variant 
on abrasive blasting uses water- 
soluble baking soda. Soda is 
amazing for paint removal and for 
fragile materials like brass, copper, 
aluminum, and glass, but not so 
good with rust. Its solubility lets 
you blast pieces and clean them up 
easily in place, without having to 
remove them from engines or other 
locations where loose grit would 
cause problems. 

• Soda blasting requires 
specialized equipment, but 
prices (without the compressor) 
have fallen below $300. 



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Remove Anything from Metal 

Step 5 — Use chemical methods. 

• "Homebrew" acids Vinegar, lemon juice, or cola can remove light surface rust. 

♦ These won't work on heavy rust or paint. Stronger acids do the job better, with no 
sugary mess to clean up later. 

• Paint remover Removes paint (duh) but not rust or corrosion. The best choice for painted, 
unrusted parts, since it won't affect the underlying metal. 

• Less effective on powder coats; for these, try multiple thick applications. 

• Alkaline rust removal (aka dip tanks or caustic dips) Not recommended. This process 
involves sodium hydroxide (lye) and chelating agent solutions that are heated to near- 
boiling temperatures. It produces nasty toxic vapors and waste, and unless you have the 
right mix of chemicals, temperature, and experience, it's not as effective as the electrolytic 
method later in the project. 



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Step 6 




• Phosphoric acid and naval jelly 

Works alone to remove light 
surface rust or as a secondary 
stage following mechanical 
treatments. 

• Heavy rust requires high 
concentrations of acid and long 
immersion, which still might not 
work on rust that has bloomed or 
turned to scale. With lighter rust, 
spray the acid and let it sit for 30 
minutes, covered with cling wrap to 
prevent drying. For faster results, 
the object should be warm. 

• Phosphoric acid is very effective 
as a secondary prep after 
mechanical treatment. It gets into 
miniscule cracks (especially on 
cast iron) and cleans out the bits of 
oxidation that even abrasive 
blasting can miss. 

• Auto parts stores carry phosphoric 
acid and zinc preps for car body 
painting (e.g., POR-15 Metal- 
Ready), which seal the metal 
surface with zinc phosphate. Naval 
jelly, which can't be sprayed, is 
strong phosphoric acid in a thick 
medium to keep it in place. 



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Remove Anything from Metal 




Step 7 — Use the electrochemical method by building your own electrolytic 
conversion tank. 



• This is a surprisingly simple way to 
remove heavy rust using DC 
electricity, a tank of sodium 
carbonate solution, and some 
sacrificial anode rods. After several 
hours of bubbling, the rust loosens 
or falls away. 

• I've used it on mechanisms so 
corroded that you couldn't even 
make out their outlines, and after 
treatment the individual parts were 
easily disassembled with hand 
tools. You can even run electrolytic 
conversion on painted rusty 
surfaces, although it takes longer. 
(See Resources in the conclusion 
section.) 

• With other homebrew electrolytic 
tanks I've seen, the objects just 
hang from a board in a 5-gallon 
bucket. I like my setup better 
because it uses plastic mesh to 
prevent short circuits between the 
anodes and the object being 
treated, and it all packs away 
neatly in the bucket. 



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Step 8 — Install the mesh ring. 




• Cut the ends off each gutter shield to make 6 pieces that just fit inside the bucket. 

• Use zip ties to connect the pieces together into a ring that lines the inside of the bucket, 
with the factory-cut ends against the bottom. 

• If your bucket is tapered, overlap the pieces to follow the taper. Trim the top portion of the 
mesh if needed to let the lid fit snugly. 



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Step 9 — Connect the rods. 




• Wind and zip-tie a length of steel wire around the top of the mesh ring, connecting it to 4 
anodes hanging down outside the mesh, one at each compass point. 

• I used 4 because the process works in a "line of sight" manner between the anodes 



and the object's surface. 

• With steel anodes, you can just tightly wrap the wire around the rod ends directly. I used 
carbon rods, which can shatter, so I attached them to the wire with small coils of softer tin 
solder. 

• Zip-tie the anodes to the mesh. 

• Finally, drill a hole in the lip of the bucket for the 2 ends of the steel conductor wire to pass 
through. 



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Step 10 — Modify the lid. 




• Drill a hole through the center of the lid and insert the threaded rod. Secure it with the 
washer and nut above the lid, and screw on the butt connector and ceiling hook at the 
bottom of the rod. 

• Drill lots more holes in the lid for ventilation — the flammable oxygen and hydrogen 
byproducts need to escape during cooking! 



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Remove Anything from Metal 



Step 11 — Put it together and zap some rust! 




• Insert the mesh ring in the bucket. The addition of the anode rods should make it a snug 
fit. Pull the conductor wires through the hole in the lip of the bucket. Construction is 
complete. 

• Set up an area with good ventilation. Fill the bucket with hot water to a level about 2" below 
the conductor wire. Add sodium carbonate, 1Tbsp per gallon of water. Stir. 

• Put your rusty object on the hook, and adjust the nut so that the object and hook are 
completely submerged when you put on the lid. 

• Connect the red (+) battery charger connection to the anode wires sticking out of the side 
of the bucket, and connect the black (-) cable to the threaded rod in the lid. 

• After about 20 seconds, lift the lid a bit and sneak a peek at the object. You should see 
some very small bubbles forming on the surface. If not, check your connections. You may 
need to scuff the rust where the object touches the hook. 

• Depending on the amperage of your DC supply, a full treatment may take up to 1 day or 
so, but you can't damage an item by leaving it in too long. 



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Step 12 



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• Remove the object and dry it. The 
visible scale and surface rust will 
have been converted to a black 
powder that can be removed with a 
wire brush, wire wheel, or light 
abrasive blasting. This oxide dust 
doesn't cling to the metal like rust. 

• Treat the object with a phosphoric 
acid and zinc prep solution. The 
acid removes any flash rust left by 
the bath, and the zinc protects 
against future rust and adheres 
well to primer. Dry, prime, and 
paint or clear-coat the object as 
soon as possible. 

• Before painting or coating, mask off 
any gear shafts, key ways, or other 
high-tolerance fittings, and swab 
gear faces and other working 
surfaces with oil so you can wipe 
the paint off later. A metal detailing 
finish can preserve the metallic 
look, and for antiquing and other 
effects, miniatures catalogs carry a 
spectrum of paints for die-cast 
figurines. 

• Before applying a clear coat, it's 
very important to remove all oils 
and other potentially corrosive 
materials. Brass, copper, and 
smooth cast iron are particularly 
sensitive to the acids in finger oils, 
and you don't want to have a 
fingerprint showing up months 
later! Wearing plastic gloves in a 
well-ventilated area, apply acetone 

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or another thin evaporative mineral 
spirit. 

• You can coat with Rust-Oleum 
spray, or try POR-15 Glisten PC 
for more durability. For enclosed 
gears and mechanisms where dust 
isn't a problem, you can also coat 
parts with way oil, a heavyweight 
oil used to grease machine tools. 



Hints and Notes 

The electrolytic bath is basic (caustic), like lye, so wear goggles and rubber gloves and keep a bucket of water or a hose 
nearby in case you spill or splash some on yourself. Alligator clip cables work well for suspending small parts like nuts and 
bolts from the hook. Painted rusty objects can take much longer because paint impedes electricity. For better results, 
scratch up the paint first, or use a paint remover before treatment. Ordinarily, you can dispose of the used bath liquid down 
the drain. But if you removed lead paint or you suspect that heavy metals (chrome in particular) have leached from your 
items, let the water evaporate to form a sludge (not a dust!) and bring it to a local toxic materials processor. 

Resources 

Metals Handbook, Volume 5: Surface Cleaning, Finishing, and Coating, American Society for Metals, various editions and 
years — an excellent general reference Wolfgang Jordan's Small Tool Museum explains the chemistry of electrolytic 
conversion. Bill's Antique Gas Engines explains the chemistry of electrolytic conversion. 

This project first appeared in MAKE Volume 17 , page 147. 

This document was last generated on 2012-11-01 01 :46:03 PM. 



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